Food and feeding behavior of Openbill Storks

Summary

1. The food and feeding behavior of Openbill Storks,Anastomus lamelligerus andAnastomus oscitans, were studied in Africa, India, Ceylon, and Thailand, during parts of 1963–68.

2. My observations and a survey of the literature indicate that shelled molluscs (principally snails of the genusPila) make up a major portion of the prey taken by both species.

3. The usual method of extracting the molluscan body from the shell is described. Most commonly the tip of the lower mandible is inserted into the shell and the body dislodged, without great damage being done to the shell. The popular notion that the open bill functions in the fashion of a “nutcracker” is not supported by my observations.

4. It is suggested that the major adaptive advantage of the open bill is that it gives the birdconvergent mandible tips, which assist in the grasping and carrying of molluscs as well as their extraction.

5. The question of whether the gap in the bill itself has any direct function and its mode and time of development could best be answered through observations and experiments on captive birds.